No effort has been made to determine whether any information in the Handbook is covered by any patent, copyright or trackmark. However, thelow magnetic permeability of austenitic stainless steels is an asset in spot or seam welding. Alternatively, the weldment ing,9th Ed. Fully austenitic stainless steels tend to be hot short, and sub- Mechanical Properties merged arc welding of these is not recommended. Sound joints may be made by either process by exerting sufficient pressure to close any voids at the weld interface and extrude all Flash and Upset Welding molten metal along with any slag or other imThese processes are commonly used to join purities.
The weld jointefficiency depends upon the ability of the welding process weldability of steel. If desired, excess solder can be removed from the joint area with a stainless steel scraping tool. Instead, gas metal arc, gas tungsten arc, or plasma arc welding should be used. Consequently, weld metal is not generally considered to be so susceptible to intergranular corrosion as the base metal. Water spots or other minor surface discolorations can be removed by scrubbing with a powdered cleanser or buffing with metal polish. Water quenching or spraying is but complete stress-relieving is not possible in necessary for thick sections, whjle ak cooling is this temperature range.
The weldability of martensitic stainless steels is affected greatly stainless steel system. However, the austenitic types suffer from heat-affected zone hot cracking that makes them very difficult to weld. Shielded Metal Arc Welding Stainless steel covered electrodes use three types of core wire: mild sfeel, stainless steel, and metal cored. Other nonstandard or proprietary alIoys are also available commercially Nickel-base filler metals are used primarily where extreme heat and corrosion resistance are required, as in jet and rocket engines, chemical processing equipment, and nuclear reactor components. Electron beam welding and laser beam welding are sometimes used. Where high strength welds are not required, standard austenitic stainless steel electrodes such as E308 or E309 can be used.
Suggested preheat, welding heat input,and poshveld requirements for martensitic Weldments made with these filler metals arenorstainkss steels mally placed in service in the as-welded condition. Preheat is but a subcritical anneal is not normally required to impmvemechmicalproperties. Phosphorus, selenium, or 303,303Se Increases machinability but promotes hot cracking during welding. Castings higher in carbonbut otherwise of generally corresponding compositionsare availablein heat resisting grades. The order of presentation has changed somewhat from the corresponding volume of the 6th Edition. Recleaning of stainless steels for brazing should include a degreasing operation to remove any grease or oil films. Postbraze Operations Flux or stop-off residue.
Insufficient pressure may cause blowholes inside the nugget, and in extreme cases, actual surface melting at the electrode. The result can be a weld with far less ferrite than specified. Also, its brazing temperafure is relatively high. Seam Welding The some limitations given above for spot welding apply to seam welding of ferritic stainless steels. Nitriding can be detected by the increased surface hardness of the metal and by metallographic examination.
These results are illustrated in Fig. Many joint designs have recessed and hidden surfaces that make post-solder cleaning to remove flux residues difficult. Resistance of stainless steel weld metal to hot cracking increases when low-melting tramp elements, especially sulfur and phosphorus, are kept at low levels. The Welding Handbook is a collective effor~of many volunteer technical specialists to provide information to assist with thc design and application of welding and allied processes. The lower heat conductivity of stainless steels produces a steeper thermal gradient than in mild steel welds. The precautions required for arc and resistance welding also apply to these processes. The nickel and manganese stabilize the austenite phase sufficiently to retain most or all of it when the steel is cooled rapidly to mom temperahue.
If not, the parts should be precoated with solder or tinimmediately after cleaning. Suggested preheat temperature, welding heat input, and postweld requirements based on carbon content are given in Table 2. This is particularly true for aluminum-bearing electrodes where aluminum is lost throughmetal-slag reactions. Improved machineability is achieved by increasing the phosphorus or sulfur content or by the addition of selenium Se ; bpes 303 and 303Se are examples. If the actual carbon content of 5pe 431 steel approaches the permissible maximum of 0. Overlap does not include any radii from forming, etc.
Base metal dilution with this process can vary from less than 10 to as much as 35 percent, exceeding that of all other consumable electrode welding processes. P Copyright by the American Welding Society Inc Thu Jul 03 14:19:03 1997. The powdered material accelerates and propagates the oxidation reaction, and also the melting and spalling action of hard-to-cut materials. . If abrasive cleaning is used for removal of flux or oxide film adjacent to the braze, sand or other nonmetallic grits should be used. The second-generation ferritic stainless steels Qpe.
Добавлен пользователем kpotik , дата Volume 7. This technique makes it easier to weld stainless steel piping. When heated to temperatures between 1500' and 1750T, transformation to austenite can be incomplete, and cooling from this temperature range results in a microstructure of ferrite and martensite. In most cases, a postweld aging heat treatment is recommended as a minimum to improve weld joint strength and reduce welding stresses. These steels are largely femtic, although welding or heat treating can result in a small amount of martensite. The fluoride residuals in slags on a weldment can be quite corrosive, and can attack the metal d u h g service at elevated temperatures. Alloying elements, including chromium, nickel, molybdenum, and columbium, can be added to the weld metal by suitable fluxes.